Telephone system



Patented Nov. 22, 1938 PATENT OFFICE TELEPHONE SYSTEM Walter Pfafl,Berlin-Zehlendorfi, Germany, as-

signer to Siemens & Halske Aktiengesellschaft,

Wernerwerk, Siemensstadt,

many

near Berlin, Ger- Applicati'on. January 2, 1937, Serial No. 118,753 InGermany February 12, 1936 9 Claims.

The present invention relates to a circuit arrangement for automatictelephone systems and in particular to telephone private branch exchangesystems in which, when all the local connectin-g devices are engaged, apublic exchange selector is set on a calling subscribers line.

In such arrangements it is known for special switching means to bebrought into operation in dependence upon the local devices beingengaged and to receive the initiating impulse for stepping the publicexchange selector and for bringing it to rest.

The invention aims at simplifying the known arrangement and achievesthis in that when the local connecting devices are engaged, the impulsefor advancing the public exchange selector and for bringing the same torest is taken up exclusively by the switching means which receive theimpulse for advancing the public exchange selector and bringing ittorest over another path in the event of free local connecting devicesbeing available.

By the arrangement according to the invention special switching meansfor receiving the impulse for stepping the public, exchange switch andbringingit to rest when the local connectingpaths are engaged, aredispensed with,

I One embodiment of the invention is shown in the drawing. It representsa private branch exi change system in which outgoing public exchangecalls can beset up in the following manner. If there are localconnecting paths, which in the present embodiment consist of callfinders AS and final selectors LW, available, a relay is ener- I gizedafter the call finder AS has been set and the final selector LW has beenset on a particular contact, which relay repeats the impulse for settingthe public exchange switch AW on the call-- ing subscribers connectionto relay RI. Relay Rt transmits the impulse for stepping the publicexchange selector and also this to rest.

If all the local connecting paths are engaged, the public exchangeselector AW' is set at once P pares .for bringing on the callingsubscriber's line. The impulseqfor stepping the public exchangeswitchanotv for bringing the latter to rest is likewise received byrelay R'I The individual switching operations are as follows: When thesubscriber at station Tn takes up his receiver the following circuit iscompleted for, the calling relay R: positive, contact: It, over the loopat station Tn, contact 2t, winding I of relay R and negative. Relay Renergizes. On account of the opening of contact 3r and the lowingcircuit is set up:

closing of contacts 41' and Sr the calling station Tn is characterizedat the testing wiper c of the call finder AS. Contact 61" completes thefollowing circuit for relay GR; positive, contacts 6r, It, relay GR, andnegative. Relay GR closes coni tact 801 so that a starting circuit iscompleted over positive, contacts 891' and 9c and lead An over which thecall finder AS is set in operation in the known manner (not shown). Thisstepping continues until the testing circuit is established over wiper cof the call finder AS. The circuit passes over: positive, relay C, wiperc of the call finder AS, contact 51', winding II of relay R, contact 41'or contact Illt, relay T, and negative. Relay T engages and breaks thecalling circuit at contacts It and 2t. At contact It the circuit isbroken for relay GR. ReIay'T also opens contact IIlt so that the testingcircuit over wiper c of the call finder AS now passes only over contact41*.

The subsequent impulse trains set the final selector LW on a particularcontact. After the setting has been completed relays AnI and P areenergized over wiper c of the final selector LW. Relay AnI closescontact IIanI so that the folpositive, resistance to, contacts I2gr, IIanl, I3b, winding I of relay D, winding I of relay RI and negative. Inthe above circuit only relay RI energizes and not relay D. Relay RIcloses contact HITI so that the rotary magnet DAW of the public exchangeselector AW is operated by relay interrupter RU. The circuit for therotary magnet DAW passes over: positive, relay interrupter RU, contactsI lrI, I505, rotary magnet DAW and negative. Relay RI has also closedcontact I61'I and has thus prepared for bringing the public exchangeselector to rest. When the public exchange selector AW has been set onthe calling subscribers line the following circuit is closed: positive,contact Ifirl, winding III of relay C5, wiper d of the public exchangeselector AW, lead IT, wiper d4 of the call finder AS, contact I810,relay FR, wiper d of the final selector LW, lead I9, and negative. Intheabove circuit relay C5 energizes and by opening contact I 505. bringsthe switch AW to rest.

The local link is released by relay FR and the known guarding (notshown) of the calling subscribers. line over wiper c of call finder ASis released. The following guarding circuit can now be. established:positive, contacts 20151", 2Ic5, winding I of relay C5, wiper c of theswitch AW, lead 22, winding II of relay R, contact 4'1", relay T'and'negative. Relay C5 energizes and switches the line through at contacts2305 and 2405. The calling subscriber receives his feeding current 55,

over relay S. Relay S energizes relay VI over contact 25s. Relay VIcloses contact 26v! so that relay B also operates its contacts. Relay 13opens contact I31) and closes contact 21b so that a further callingimpulse on the part of a subscriber again operates on the relay RI ofthe public exchange selector AW shown, but is transmitted over contact211) to the second public exchange selector. Relay S can receive theimpulses for setting the public exchange connecting devices and repeatsthem over the public exchange line at contact 28s.

If all the local connecting devices are engaged all the C relays of thecall finders serving the local traffic are energized. Thus the chainover contacts 290, 30cI, etc., is completed. If now when all the localconnecting devices are engaged the private branch exchange subscribertakes up his receiver the calling relay R and in consequence relay GRbecome energized in the manner described. Relay GR establishes thefollowing circuit: positive, contacts Bgr, 29c, 30cI, 3Iab, 32anl, I3b,winding I of relay D, winding I of relay RI and negative. Relay RIcompletes the circuit for the rotary magnet DAW in the manner alreadydescribed and prepares for bringing the public exchange selector to restby closing contact IIirI. When the public exchange selector AW is set onthe calling subscribers line the testing circuit passes over: positive,contact lBrI, winding III of relay C5, wiper d of the switch AW, leadI'I, contacts 3315, 51', winding II of relay R, contact 41', or IIlt,relay T, and negative. Relay T energizes and as already described breaksthe calling circuit and the circuit for relay GR. The public exchangeselector is brought to rest by relay C through the opening of contactI505 and the guarding circuit is set up over contact 2| c5. At the sametime the line is switched through at contacts 2305 and 2405.

As may be seen from the foregoing description, special switching devicesfor setting the public exchange selector on a calling subscribers linein the event of all the local connecting devices being engaged areabsolutely unnecessary.

When the impulse for setting the public exchange selector, in the eventof all the local connecting paths being engaged, is received by relayRI, relay D energizes. Relay D locks up over: positive, contacts 3405,35d, winding II of relay D and negative. By opening contacts 36d and3'Id and closing contacts 38d and 39d dial tone we is applied to thespeaking leads to inform the calling subscriber that he can commence todial.

This dial tone may be difierent from the usual dial tone so that thecalling subscriber is thereby informed that he has been connected to apublic exchange line.

When the subscriber dials the number of outgoing calls the impulsestransmitted from the subscriber at station Tn are received by relay Sand then repeated to the rotary magnet DML. The circuit for magnet DMLpasses over: positive, contacts 401) I 4Is, rotary magnet DML andnegative. Through the impulse train, relay V2 is engaged over: positive,contacts 428, and 4312i, relay V2 and negative. When at the end of theimpulse train relay V2 releases the following circuit is establishedprovided that the digit characterizing outgoing public exchange callshas been dialled: positive, contact 44122, wiper a of the switch ML inthe position corresponding to the characterizing digit for outgoingpublic exchange calls, lead 45, contact 46d, winding III of relay D,winding II of relay D and negative. Winding III of relay D is arrangedso as to oppose the effect of winding II so that relay D is caused torelease by means of the counterwinding III. Relay D opens contacts 38dand 39d. This switches the public exchange line through.

If the subscriber dials a digit other than the digit for outgoing-callswiper a of the switch ML passes to a position in which winding III ofrelay D is not connected up. Relay D then remains energized and preventsthe public exchange line from being switched through at contacts 36d and31d. The subscriber receives the signal telling him that for the timebeing all the local connecting paths are engaged. The calling subscriberreplaces the receiver and thereby causes the devices which have beentaken into use to be restored. The public exchange selector AW isrestored to normal in the known way through the release of relay S.Relay C5 deenergizes and completes a circuit over: positive, relayinterrupter RUI, contact 4105, wiper b of the switch ML in the workingposition, rotary magnet DML and negative. The rotary magnet DML isoperated until the switch ML reaches the normal position. Thereupon allthe switches which have been taken into use are once more in the normalposition. The arrangement could also be modified by connecting thepoints 44/48 so that after a digit other than that characterizing publicexchange calls has been dialled a relay TR is energized over wiper a ofswitch ML and the multiple connected empty contacts, which relay byopening the guarding circuit at contact 20 brings about the release ofrelay C5 and thus releases the public exchange selector AW.

What is claimed is:

1. In a private branch telephone system wherein a main exchange selectorconnects with a calling line when all local connecting lines are busy,switching means associated with said selector, means including all ofsaid busy connecting devices for preparing said switching means foroperation, said switching means operated thereafter responsive to animpulse transmitted by the initiation of an additional call to startsaid selector stepping to find the calling line and for preparing a stopcircuit for terminating the stepping of said selector when the callingline is found, and means responsive when a connecting device is idle anda trunk call is initiated thereover by a calling subscriber fortransmitting an impulseto operate said switching means to control saidselector in identical manner.

2. In a system as claimed in claim 1, in which said switching meansincludes a relay operated by an impulse transmitted by the initiation ofa call when all of said connecting devices are engaged or when a trunkcall is extended over an idle connecting device.

3. In a system as claimed in claim 1, a testing circuit for saidselector including a wiper thereof, said testing circuit testing for acalling line as the wipers of said selector are advanced and completingthe stop circuit to terminate the stepping of said selector when thecalling line is found, said testing circuit being identical for findinga calling line when idle connecting devices are available or when all ofsaid connecting devices are engaged.

4. In a private branch telephone system wherein a main exchange selectorconnects with a calling line when all local connecting devices are busy,switching means for starting said selector stepping, means including allof said busy connecting devices for preparing said switching saidselector and said line nating the stepping of said selector when saidmeans for operation, a calling subscribers line equipment, meanscontrolled by said line equipmentwhen a call is initiated at a time allof said connecting devices are busy for transmitting an impulse foroperating said switching means, and a testing circuit including a wiperof equipment for termicalling line equipment is found.

5. In a private branch telephone system wherein a main exchange selectorconnects with a calling line when all local connecting devices are busy,switching means for starting said selector stepping, means including allof said busy con-- necting devices for preparing said switching meansfor operation, a calling subscribers line equipment, means controlled bysaid line equipment when a call is initiated at a time all of saidconnecting devices are busy for transmitting an impulse for operatingsaid switching means, a testing circuit including a wiper of saidselector and said line equipment for terminating the stepping of saidselector when said calling line equipment is found, means responsivewhen any one of said connecting devices are idle and a call is initiatedfor controlling said idle connecting device to find the line equipmentof said calling line, means controlled by said calling subscriber forcontrolling said connecting device to initiate a trunk call, meansoperated responsive to the initiation of a trunk call for transmittingan impulse for operating said switching means, said testing circuit nowincluding a wiper of said selector and said connecting device forterminating the stepping of said selector when said calling line isfound.

6. In a system as claimed in claim 1, a register in said selector, aspecial relay, said special relay included in series with said switchingmeans and operated in series therewith only when all of said connectingdevices are busy when an additional call is initiated, and meanscontrolled by the operation of said special relay for placing saidregister under control of the calling line.

7. In a private branch telephone system wherein a main exchange selectorconnects with a calling line when all local connecting devices are busy,switching means associated with said 3 selector, a special relayincluded in series with said switching means, means including all ofsaid busy connecting devices for preparing said switching means and saidspecial relay for operation, said switching means and said special relayoperated in series thereafter responsive to an impulse transmitted bythe initiation of a call by a subscriber, means controlled by theoperating of said switching relay for starting said selector stepping tofind the line of the subscriber initiating said call and for preparing astop circuit for terminating the stepping of said selector when acalling line is found, a register associated with said selector, meanscontrolled by the operation of said special relay for connecting saidregister to said selector, a trunk line to a public exchange terminatingin said selector, means in said selector controlled bysaid callingsubscriber for setting said register, and means controlled by thesetting of said register for either extending said calling line throughto said trunk line by way of said selector or for preventing theextension of said calling line to said trunk line.

8. In a system as claimed in claim 7, in which a release relay isprovided for said selector, said release relay operated responsive tothe setting of said register to a position other than the positiondetermining a trunk call to restore said selector to normal.

9. In a telephone system, subscribers lines, a plurality of connectingdevices controllable by said calling subscribers to extend localconnections, a trunk line to a distant exchange, a selecting devicehaving access to said subscribers lines terminating said trunk line,switching means associated with said selecting device, a chain circuitfor preparing said switching means for operation when all of saidconnecting devices are engaged, means for operating said switching meansto start said selecting device stepping to find a calling subscribersline responsive to an impulse transmitted over said chain circuit by theinitiation of an additional call, means in said selecting deviceoperated responsive to thefinding of the calling line for terminatingthe stepping thereof, and means in said selecting device controlled bysaid calling subscriber for extending a connection over said trunk line.

WALTER PFAFF'v

